ProFlo Performance’s 632ci big-block Chev

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How good are cubic inches? Sure, highly strung aspirated small-blocks, forced induction and fancy modern engine architecture all have their place, but there’s a lot to love about a big old naturally aspirated fat-block, especially in a regularly driven street car.

First published in the September 2026 issue of Street Machine

By virtue of its sheer cubic capacity, this ProFlo Performance-built 632ci rat motor doesn’t need to rely on exotic race fuels, bulk rpm or a high-maintenance valvetrain to make decent steam. Built with off-the-shelf bits, it should be handy for 900hp on pump fuel, all day, every day.

To a Dart Big M block, ProFlo added a Scat crank and rods and 12.5:1 JE slugs, and slid in a custom hydraulic-roller camshaft specced for spirited street duties, with .630in lift and 264°/274° duration. The heads are AFR 385 alloy units loaded with Comp Cams Ultra Pro Magnum rockers, providing ample airflow and looking very shiny indeed.

Oiling is a straightforward affair with a Milodon pan and Melling Select pump, and it looks pretty as a picture topped with Shaun’s Custom Alloy valve covers.

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GREEN IS NICE: You may have already picked it, but the Verdoro Green paint on the block has been applied to match the HT GTS Monaro for which this engine is destined. “It’s a mini-tubbed, four-linked street car, which will be the kind of thing that the customer can just hop in and drive on the weekends,” says Paul.

These are all fairly basic, speed shop-available parts, so it’s a simple recipe for more power than the customer will ever need for the street.

The fancy bit is the Kinsler Dragon Claw V2 stack injection manifold – what a beauty! Word is it wasn’t exactly cheap, but the fearsome mechanical look harks back to the golden era of pro street, yet it’s EFI-ready out of the box to further assist with the impeccable street manners this engine needed to deliver.

“It came with the TPS, fuel rails, injector ports and the vacuum stuff for EFI all pre-done,” says ProFlo boss Paul Sant. “On the ignition side, we have an MSD crank trigger with a PFP billet bracket, and we’ll use eight LS coils with a FuelTech running it all.”

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This particular engine is yet to see the dyno, but a near-identical package by ProFlo has delivered 900hp in the past. That’s hard to beat for something you can jump in, hit the key and drive, and fill up at a servo on your way to the pub for a countery.

Maybe there really is no replacement for displacement after all?